Robin Thicke and girlfriend April Love Geary expecting second child

Robin Thicke and girlfriend April Love Geary are expecting their second child together, Geary revealed on Instagram Tuesday. (Getty Images)

Robin Thicke is about to become a father of three.

The 41-year-old singer's girlfriend, April Love Geary, is pregnant with their second child together. The expecting mother shared the exciting news on her Instagram on Tuesday, alongside a video and photo of the couple's 6-month-old daughter, Mia, holding a black-and-white photo of the sonogram.

"Well someone is going to be a big sister next year! We’re so excited to share with y’all that I’m expecting again! 😇," Geary captioned the sweet shot. "We find out Saturday if it’s a boy or a girl! What do you guys think it’s going to be?"

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Thicke and Geary, 23, welcomed daughter Mia in February. The "Blurred Lines" singer is also dad to an 8-year-old son, Julian, with his ex-wife, Paula Patton.

On Monday, Thicke shared a sweet video of himself holding Mia while watching baseball.

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In March, the model also shared a picture of Julian and Mia snuggling.

"MY HEART! I am so blessed!" she wrote. "Julian is such an angel to his little sister. He sings to her, reads her books and holds her until his arms get sore! I love my little family ♥️."

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Patton also told ET in April that her son Julian loves being a big brother to Mia.

"It's a great thing," Patton said. "I think that family, no matter what -- divided, [or if] it's in new places -- you have to find harmony and peace for your children. He is in that place right now and it's a beautiful thing to see. He absolutely adores his little sister Mia."